若x²+3x-(1/3)=0,
x²+3x=1/3
则代数式（x-3）/3x²-6x÷[x+2-﹙5/x-2﹚]
=（x-3）/3x(x-2)÷[((x+2)(x-2)-5)/(x-2﹚]
=（x-3）/3x(x-2)÷[(x^2-4-5)/(x-2﹚]
=（x-3）/3x(x-2)÷[(x^2-9)/(x-2﹚]
=（x-3）/3x(x-2)*(x-2)/(x+3)(x-3)
=1/3x(x+3)
=1/3(x^2+3x)
=1/(3*(1/3))
=1